In a multi-cell battery pack, cells may differ from each other due to cell aging and different cell temperatures. A voltage difference between the cells may increase as the number of charging/discharging cycles increases, which may cause imbalance between the cells and may shorten a battery life.
During a time period when the battery pack is discharged with a relatively high current, if the imbalance between the cells reaches a certain limit, a voltage reversal on the weakest cell may result in permanent damage for the weakest cell.